Most of the widely used nitrogen source fertilizers provide the soil with ammonium nitrogen. These fertilizers include liquid ammonia, urea, and ammonium salts such as ammonium sulfate. Upon addition to the soil they form ammonium ions which act as a suitable nitrogen source for cultivated crops. Urea nitrogen is rapidly hydrolyzed in soil to ammonium nitrogen. The ammonium form of nitrogen is positively charged and is attracted to the negatively charged soil particles. Thus this form of nitrogen is sorbed by the soil while remaining available for plant utilization.
However, soils contain nitrifying bacteria which can act on the ammonium converting the nitrogen to the oxidized forms of nitrite and nitrate. Oxidized forms of nitrogen are negatively charged so they are not attracted to the soil particles. Being soluble in water they can be lost by leaching into the ground water. Loss can also occur by the action of denitrifying bacteria which convert nitrate to gaseous forms of nitrogen which enter the atmosphere.
For the purpose of conserving ammonium nitrogen in soil, the practice has therefore developed of adding compounds to soil which act as nitrification inhibitors, sometimes referred to as nitrificides. They act to inhibit nitrification of ammonium nitrogen by nitrifying bacteria.
In commercial practice in the United States two nitrificides are in primary use. One of these is the compound etridiazole (5-ethoxy-3-trichloromethyl-1,2,4-thiadiazole), which is sold under the trademark "Dwell" by Olin Corporation, Little Rock, Ark. The other compound is nitrapyrin which is sold under the trademark "N-Serve" by The Dow Chemical Company, Midland, Mich. The full chemical name of nitrapyrin is 2-chloro-6-(trichloromethyl) pyridine. These commercial inhibitors are relatively complex, expensive chemicals.
Acetylenic alcohols comprising substituted propynols have been proposed as soil nitrification inhibitors, but are not known to have been used commercially. See U.S. Pat. No. 3,033,668. The 1-substituted-2-propyn-1-ols as described in the cited patent include alkyl, alkenyl, phenyl, aralkyl and other substitutions.
It has been shown that acetylene (C.sub.2 H.sub.2) in a closed system will inhibit nitrification of ammonium nitrogen in soil. Walter et al (1979) Soil Sci. Soc. Am. J., 43: 195-196; and Bremner et al (1979) Nature, 280 (5721): 380-381. However, acetylene is not a practical nitrificide for field use. It is explosive gas, which would be difficult and dangerous to apply, and which would not be retained in the soil.